<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    body {
      height: 200px;
      border: 1px solid #000;
    }
    .box {
      width: 100px;
      height: 100px;
      background: red;
      margin: 50px auto 0;
      transition: 1s;
    }

    body:hover .box {
      transform: scale(.5);
    }
  </style>
</head>

<body>
  <div class="box">111</div>
</body>

</html>